1. Field of The Invention
This invention relates to a thermal transfer system which is, for example, adapted for use in color video printers. The invention also relates to a printing paper and an ink ribbon particularly Useful in the thermal transfer system.
2. Description of The Prior Art
Thermal transfer printing systems are known in the art in which images are obtained by heating an ink layer which contains a dye and is supported on a substrate, thereby melting and diffusing the dye in an imagewise pattern so that the dye is transferred on an image-receiving layer of a printing paper mainly composed of a resin. Intensive studies have been hitherto made on thermal transfer printing materials used in the system in order to improve the light fastness of the printing materials to an extent as close as that of silver salt photographs. For instance, attempts have been made to add UV absorbers and/or antioxidant agents to the image-receiving layer.
However, the UV absorber is not so effective unless the absorber is provided as an upper layer below which the dye is received. When the UV absorber is added to a laminated layer, its effect is lasting but with the disadvantage that a printing time is prolonged.
On the other hand, antioxidant agents may be effective for specific types of dyes. However, several types of dyes are used for yellow, magenta and cyan colors and existing antioxidant agents are not effective for all of these dyes. In an extreme case, antioxidant agents may expedite degradation of dyes. Further studies have been made on the structure of dyes and the type of resin used for the image-receiving layer, with an attendant problem that there has not been obtained yet any thermal transfer system comparable to silver salt photographs.